Notes Payable and Credit Agreements (Tables)

12 Months Ended

Sep. 30, 2021

Short Term Borrowings [Abstract]

Schedule of Short-term Borrowings

Information about short-term borrowings, including Spire Missouri’s and Spire Alabama’s borrowings from Spire, is presented in the following table. As of September 30, 2021, $348.5 of Spire’s short-term borrowings were used to support lending to the Utilities.

	Spire (Parent Only)						Spire Missouri						Spire Alabama			Spire
	CP			Term			Term			Spire			Spire			Consol-
	Program			Loan			Loan			Note			Note			idated
Year Ended September 30, 2021
Highest borrowings outstanding	$	775.0		$	150.0		$	250.0		$	441.9		$	152.2		$	850.5
Lowest borrowings outstanding		140.0			—			—			95.3			—			390.0
Weighted average borrowings		448.1			31.6			130.8			303.2			33.2			610.5
Weighted average interest rate		0.2	%		1.1	%		0.7	%		0.2	%		0.2	%		0.4	%
As of September 30, 2021
Borrowings outstanding	$	422.0		$	—		$	250.0		$	240.9		$	49.0		$	672.0
Weighted average interest rate		0.2	%	n/a				0.7	%		0.2	%		0.2	%		0.4	%
As of September 30, 2020
Borrowings outstanding	$	498.0		$	150.0		$	—		$	301.2		$	121.3		$	648.0
Weighted average interest rate		0.2	%		1.1	%	n/a				0.2	%		0.2	%		0.6	%